A surgical adhesive is used in lieu of physical means, such as sutures or staples, to bind together two edges or sides of a laceration. Biologically and non-biologically based surgical adhesives are made by mixing a first reactive fluid component (e.g., fibrinogen) with a second reactive fluid component (e.g., thrombin), which react with each other to harden into the adhesive. Upon contact the two fluid components react relatively quickly, in the order of seconds, to harden into the tissue adhesive. If it is only partially mixed, the adhesive will not sufficiently harden over the entire area to which it is applied thus, resulting in weak spots. It is, therefore, desirable to apply a thoroughly mixed solution to the target site before the solution has gelled or hardened. Furthermore, it is desirable to minimize the amount of time required to thoroughly mix the fluid components together, thereby minimizing the amount of contact time between the two substances prior to delivery to the target site.
Several methods and devices exist for mixing and applying biologically based and synthetic tissue adhesives. One method is to directly apply a layer of the first fluid component to the target site, directly apply a layer of the second fluid component on top of the first fluid component layer, mechanically mix the two fluid components together using a surgical instrument and spread the mixed adhesive over the target area. A variation of this method is to premix the two fluid components, immediately thereafter draw the adhesive mixture into a delivery syringe and apply the mixture to the target site. Both of these methods suffer from multiple deficiencies, not the least of which is that it is very difficult to thoroughly mix the fluid components and apply the mixed adhesive before the adhesive begins to gel and harden, resulting in a nonuniform adhesive layer with weak spots.
More recent devices and methods utilize one device for bringing the fluid components together, mixing the fluid components and applying the mixed adhesive in either an aerosol or a stream form to the target site. The more recent devices and methods can be broken down into two general types: 1) devices that bring the two fluid components together, mix them within the device and then dispense the mixed adhesive; and 2) devices that separately atomize the two fluids outside the device such that the atomized fluids contact and mix together before being deposited on the target site.
An example of the first type is described in U.S. Pat. No. 4,735,616 to Eibl et al. This device has two parallel fluid component syringes fluidly connected to two channels that extend through a manifold into a mixing needle. The two fluid components flow through their respective channels and enter the mixing needle, where they contact for the first time. The high surface area within the mixing needle creates turbulents that cause the fluid components to become thoroughly mixed within the needle. A second example of this type of device is described in U.S. Pat. No. 5,116,315 to Copozzi et al. This device has two parallel fluid component syringes connected to one end of a Y-manifold and a mixing assembly detachably locked onto the second end of the Y-manifold. The mixing assembly has two separate and adjacent parallel channels, each separately fluidly connected to the two fluid component syringes, via the Y-manifold, and both of which terminate into a single annular channel within the mixing assembly. The annular channel is connected to a disk shaped mixing space having three inclined vanes disposed about an exit orifice. In use, the two fluid components pass through the Y-manifold, through the two separate parallel channels in the mixing assembly, through the singular annular channel, where the fluid components first contact and begin mixing, through the mixing space, where the fluid components impinge upon the vanes that impart a spiraling motion to the fluids causing the fluids to become thoroughly mixed, and out of the exit orifice in an atomized spray. A problem experienced with these types of devices is that they typically become clogged after a short period of non-use, because the un-ejected, mixed or partially mixed, adhesive hardens within the device.
An example of the second type of devices is described in U.S. Pat. No. 5,368,563 to Lonneman et al. Similar to the first type of devices, Lonneman et al. disclose a device having two parallel syringes connected to a manifold. However, the manifold has two separate exit orifices adjacent and in close proximity to each other. In use, the two fluid components exit from the corresponding exit orifices in a swirling atomized spray. The atomized fluid components mix with each other while airborne without the need for an internal mixing chamber. While the Lonneman et al. design alleviates the clogging problem of the first type of devices, it has been found that it does not adequately mix the two fluids, particularly at the peripheries of the two atomized spray cones, thus resulting in an adhesive layer having weak spots.
There thus remains a need in the art for a device that can thoroughly mix the reactive fluid components of a tissue adhesive and deliver the mixed adhesive to a target site without clogging after only a single use.